1. Field of the Invention
The present invention relates to a method for forming various patterns such as conductive patterns on a surface of a base material and a wired board having conductive patterns.
2. Description of the Related Art
The wired member, which includes, for example, boards or substrates on which electronic devices such as IC chips are mounted, and flexible printed circuits (FPC) which are usable to electrically connect devices, has a conductive pattern which is formed on a surface of a base material composed of, for example, a silicon material, a glass material, or a synthetic resin material. It is preferable that such a conductive pattern is formed to have a width and a pitch which are as fine as possible, for example, because it is intended to miniaturize the sizes of the board and the wired member.
The lithography method has been hitherto used as a method for forming the fine conductive pattern as described above. In the case of the lithography method, a conductive film is formed on a board surface, and then a resist is further applied thereto. A pattern is developed on the resist, and then the resist, which is disposed at portions other than the pattern, is removed. The conductive film is removed from the area in which the resist has been removed, for example, by means of the etching to form the conductive pattern. However, in the case of the lithography method, it is necessary to perform a plurality of steps. Therefore, the apparatus or equipment is large-sized, and the production cost is expensive as well.
In view of the above, some methods are known to form conductive patterns conveniently. For example, U.S. Pat. No. 6,973,710 B2 (FIG. 6) and United States Patent Publication No. 2005/0158456 A1 (FIG. 6) (corresponding to FIG. 6 in Japanese Patent Application Laid-open No. 2002-261048) describe a method for forming a conductive pattern, in which a plurality of lengthy holes or grooves corresponding to a desired pattern are formed for a base material, and then a conductive liquid is jetted onto the base material from a nozzle of an ink-jet head into the holes or the grooves to form the conductive pattern.
In the case of the method for forming the pattern described in U.S. Pat. No. 6,973,710 B2 and United States Patent Publication No. 2005/0158456 A1, it is necessary that the width of the lengthy hole or the groove is larger then the diameter of the liquid droplet jetted from the nozzle, because the conductive liquid is directly landed on the lengthy hole or the groove from the nozzle of the ink-jet head. In other words, it is impossible to form any conductive pattern which has a width smaller than the liquid droplet diameter. Therefore, there is a certain limit even when it is intended to decrease the width of the conductive pattern.